In recent years, there have been increased use cases where a plurality of people perform simultaneous operation or simultaneously look at a document. For example, a plurality of people surround a large screen (wall-surface display unit, electronic board, or the like) or a table top (table-type image display device) and conduct a meeting while looking at a document displayed on an image display device.
Regarding such an image display device that can be viewed by a plurality of people, for example, Patent Literatures 1 and 2 described below are proposed. Specifically, there are proposed techniques for, in the case where a table-type image display device displays an object serving as a document of a meeting on a display and participants of the meeting have discussions on the basis of the same object, displaying the object while enlarging the object (Patent Literature 1) or separating the object (Patent Literature 2) so that the participant who have discussions can clearly look at the object.